Words used by the driver, having finished, getting out of a bus (5)
I believe the answer is:
verbs
'words' is the definition.
(verb is a kind of word)
'the driver having finished getting out of a bus' is the wordplay.
'the driver' becomes 'v' (I can't explain this - if you can you should believe this answer much more).
'having' says to put letters next to each other.
'finished' becomes 'up' (eg 'time's up' means the time is finished).
'getting out of' indicates named letters should be taken away.
'a' becomes 'per' (eg 'one a day' means 'one per day').
'per'+'bus'='perbus'
'perbus' with 'up' removed is 'erbs'.
'v'+'erbs'='VERBS'
'used by' acts as a link.
Can you help me to learn more?
(Another definition for verbs that I've seen is " Parts of speech".)